Development of an effective technology for hydrometallurgical processing of zinc cakes by Almalyk MMC JSC

Currently, much attention is being paid to the more complete extraction of valuable components of zinc-containing raw materials, the application of waste-free technology, and the production of pure zinc of the highest grade in zinc production. Hydrometallurgy is an effective method of processing zinc concentrates. This method is also used in Almalyk MMC JSC. In accordance with this method, the cinder obtained after the oxidative roasting of zinc sulfide concentrates is subjected to sulfuric acid leaching. In this case, a zinc sulfate solution is formed, which, after purification, is sent to the electrolysis shop to obtain zinc cathode. Also, a solid residue (a recycled product) is formed in the process — zinc cake with a high content of zinc (18–24%) and copper (0.3–1.5%), which are in the form of insoluble ferrites. The main method of cakes processing is the Waelz process. In Almalyk MMC JSC, the Waelz process is carried out in rotary tube furnaces. The disadvantages of the process include the high consumption of imported expensive coke: 492 kg is consumed per 1 ton of cake. In order to exclude the expensive Waelz process, research work has been carried out on the processing of zinc cakes by the hydrometallurgical method. The process of high-temperature sulfuric acid leaching has proven itself well in the processing of zinc cake, ensuring the selectivity and complexity. The optimal mode of the process: the duration of leaching is 4–4.5 hours, the concentration of sulfuric acid is 180–190 g/l, the leaching temperature is 90 oC. The end-to-end extraction of zinc into the solution is 97–98.5%, copper — 92–93%. The obtained sulfuric acid solution contains, g/l: zinc — 53.4; copper — 4.28; iron — 14.8.